Calling Nailhead Experts!

Okay I think I have finally zeroed in on a motor for my project. I am interested in a Buick Nailhead engine. My experience is pretty much all with SBC engines so this is venturing out of my base of knowledge. So I thought I would post a thread here and get some feedback from the HAMB community.

1) Is there any advantage disadvantage of going with the 401 versus the 425. My general impression is the 425 is harder to find and carries a price tag premium just because its "bigger."

2) Would you start from a good core and build up or buy something completed oil pan up to intake? I have seen a couple of motors on HAMB as well as Ebay etc. that are almost complete motors. The prices have ranged any where from $850 to $3500.

3) How much should I budget for a Nailhead build? I will either be going with a four barrel carb or three deuce setup.

4) Are there any special things I should do or not do?

5) Can you recommend someone with Nailhead expertise should I decide to have one built?

6) What transmission can I use? I have seen some bell housings that adapt to MUNCIE for example.

Thanks for the tips guys.
Kevin

 

This will be good, I'm going to wait and see what people say. I build engine for a living, and just got through with a 425 2x4 motor. I want to see if I'm in line with other people. The Buick is a good engine, Buick was the only one with GM that test the engine before they installed them in new Buick back then. Lots of torque. 401 had 445 pounds of torque and the 425 had 465. Well built block. Steel crank and rods. If they don't tell you what you want to know. E mail me and I[ll try to help.

 

They are quite a bit more expensive to rebuild, but the biggest problem is coming up with a transmission.

 

I paid $800 for my 1965 401 out of a running Electra. It came with the TH-400 auto. This was four years ago in preparation for my Hot-Rod project.

I plan to go through it and check it out, for peace of mind, and maybe get it hopped up with a cam and some clean/blending work on the heads due to the casting flash. I have the stock 4bbl intake and want to step up to a dual quad eventually. Outside of that, I am also a newbie and am doing research so I only have to do this once.

I also just acquired an M-20 and Bendtsen's Nailhead adapter kit. Wilcap also sells a bellhousing adapter for 4 and 5 speeds, from what I have read. I have a storage room full of parts and places like the HAMB, Nailheaders on yahoo groups, and v8buick.com to help me figure out the rest.

Good luck on your project, cause I sure as hell know I need it now.

 

From what I understand...a 425 is a pretty thinwall casting and cannot take too large of an overbore. So if you have a scratched cylinder or it has already been rebuilt you might have to sleeve it....which is fine but costs extra bucks. The 401 can be bored out no problem...in fact I think the 425 is a bored 401...they have the same stroke..the 401 is a 4.1875" bore and the 425 is a 4.3125" bore...that .125" difference is meat the 425 block doesnt have....The 401 you have is a good choice and you got one of the best transmissions known to man...

 

1. 401 is fine. Don't sweat the 24 cubes.

2. Start with a good core, well unless a fresh rebuild falls in your lap. Expect to pay close to a grand for a good one. This could get you a runner, but I'd still go through it.

3. Depends. Are you paying someone to do it, or are you going to do a lot of the work? Parts wise you could be into it for anywhere from $1200-3500 depending.

4. Don't let anyone talk you into hardened valve seats, if they try they DO NOT know Nailheads and walk away.

5. Not sure in where in Texas, I'm sure Crushproof in Austin could help out. Otherwise it's a long distance deal.

6. Manual transmission bellhousing from Bendsten's, otherwise ST400 or SP400 from a 64-66 Nailhead equipped Buick.

Guides really have no issues with unleaded fuel, and in this instance neither do the seats. DO NOT try and put hardened seats in these heads. Low spring pressure and high nickel content negate the need. That and the water jackets being so close you will ruin the heads.

 

One thing I almost learned the hard way is that all nailheads are externally balanced. SOme of the aftermarket flywheels like EELCO are nuetral balanced as delivered, so you have to have the entire rotating assembly re-balanced with the new flywheel. So the best flywheel option seems to be to go find a stocker flywheel to use.

Also, the 364's had a different amount of external balance weight than the 401/425/322's so don't try to use a 364 flywheel on a 401... The 364 has a larger crank snout than the later nailheads, but the early 401's also had the larger crank snout (what the flywheel will pilot on), so be carefull you don't put a 364 flywheel on your 401.

Good luck!
Matt